The present embodiments relate to wireless communications systems and are more particularly directed to a wireless communication system with a highly flexible and integrated base station that operates in part to perform processor requested RAKE finger tasks.
Wireless communications have become prevalent in business, personal, and other applications, and as a result the technology for such communications continues to advance in various areas. One such advancement includes the use of spread spectrum communications, including that of code division multiple access (“CDMA”). In such communications, a user station (e.g., a hand held cellular phone) communicates with a base station, where typically the base station corresponds to a “cell.” CDMA systems are characterized by simultaneous transmission of different data signals over a common channel by assigning each signal a unique code.
CDMA includes various different operating modes and standards that are introduced here because they are also supported in the preferred embodiments. The modes include a 1×RTT mode sometimes referred to in the art as Radio Configuration 3 and 4 (“RC 3&4”), and an IS95 mode sometimes referred to in the art as Radio Configuration 1 and 2 (“RC 1&2”). In addition, CDMA continues to advance along with corresponding standards that have brought forth a third generation CDMA also referred to as 3G cellular. 3G cellular includes two standards, namely, IS2000 which is Qualcom based and supports IS95 in one operational mode, and a wideband CDMA which is also referred to as WCDMA and which has a 3GPP standard.
With respect to base station operations in various CDMA systems, the base station generally receives and manages signals from numerous different user stations. Typically, the user stations are mobile and for this and other reasons the signals received by the base station from the user station are subject to various effects imposed on the signal as they are communicated to the base station. In addition, CDMA signals are modulated, or “spread,” with one or more pseudo-noise (“PN”) codes, such as a short code, a long code, and possibly a Walsh code based on the type of symbol being communicated as well as the operational mode. Accordingly and with the advancement and evolution of CDMA, base stations are known in the art to include sufficient circuitry to demodulate, or “de-spread,” such codes from the communication. The prior art typically includes complex multiplication and accumulation circuits that are physically duplicated to process different received signals at the same time, thereby deciphering the symbol information encoded in those signals. This process is commonly performed by a device that is part of the base station and that is referred to as a RAKE receiver; the RAKE is said to have fingers and each finger is assigned to process an incoming signal. The decoded symbols may represent multiple paths from a single transmission by the same user station, as further detailed below. Accordingly, prior art base stations often include circuitry to separately identify and process these multiple paths and also to combine the signals in an effort to improve signal performance (e.g., as measured by signal-to-noise ratio, bit error rate, or some other type of measure).
While the above-discussed state of the art has supported usable spread spectrum communications, the present inventors have observed various drawbacks. For example, presently in the prior art, a RAKE receiver may include duplicate physical circuits representing the different fingers of the RAKE, and often certain duplicate information (e.g., de-spreading codes) are hard-coded or stored in multiple locations so as to be provided to each finger. The duplicate circuits as well as the need to duplicate information is inefficient in many respects, such as increasing device size, complexity, and cost. Such attributes are often highly undesirable and indeed sometimes unacceptable in the continued advancement of the competitive market for cellular devices. As another drawback, various prior art RAKE devices have fixed uses and thus lack programmability. Accordingly, they are relatively inflexible or require considerable re-design if it is desired to operate the system with different parameters. Still other drawbacks and limitations may be observed by one skilled in the art.
In view of the above, there arises a need to provide an improved wireless system, as is achieved by the preferred embodiments discussed below.